Injection moulding is a common manufacturing process for producing components, such as plastic, silicone, metal or rubber components.
A conventional injection moulding assembly comprises two sections which each support a mould half. The sections are joinable by means of a unit intended for the purpose.
For injection moulding of a component, the sections, and thus also their mould halves, are brought together. The mould halves define in their joined state a cavity. A melt is introduced under pressure into the cavity and, after the necessary cooling, the sections can be divided and the completed component be ejected.
When introducing the melt into the cavity, a dividing force arises, which acts to divide the mould halves. This dividing force is the product of the pressure at which the melt is introduced into the cavity, and the surface area projected parallel to the parting plane of the mould halves. To prevent such separation of the mould halves, it is thus necessary for the mould halves to be held together by means of a locking force that is not less than said dividing force.
To achieve a high production capacity, it is common for the mould halves to define a plurality of cavities, thereby making it possible to produce a plurality of components during each injection moulding shot. Of course, the projected surface area will be larger. At an unchanged pressure, the dividing force will thus be higher.
The unit that acts to bring together the sections has a limited maximum locking force, by means of which it can hold together the sections, and therefore this unit is a limiting factor to the production capacity that can be achieved in the injection moulding assembly.
If a higher production capacity is desired, resulting in a dividing force which is higher than this maximum locking force of the unit, the components must be produced in a larger and, thus, also considerably more expensive injection moulding assembly.
CH653286 discloses a mould which to some extent solves this problem. The mould comprises a valve means which ensures that the melt during an injection moulding shot is in turn passed to separate groups of cavities. Owing to the fact that all cavities are not filled at the same time, the dividing force can be retained at an advantageously low level. However, the problem of this solution is that it necessitates a valve means, which can affect the flow configuration of the melt and, thus, also the final quality of the injection moulded components. It will also be appreciated that such sequential filling of the cavities results in the injection moulding cycle taking more time, which has a detrimental effect on the production capacity.
DE3937473 discloses an injection mould for production of undercut components. The mould comprises two semicircular mould halves, which are brought together to define a cavity together with a core. The mould halves are locked in their joined state by means of a sleeve which has an inner conical surface and which is passed over the joined mould halves, which have a complementary outer conical surface. There is no indication of how an increased production capacity is to be achieved.